Thanks a lot Marcus
Dor
בתאריך יום ד׳, 5 ביולי 2023, 7:33 אחה״צ, מאת Marcus D. Leech <
patchvonbr...@gmail.com>:
> On 05/07/2023 01:18, Dor Ratz wrote:
>
> Hey Marcus
>
> In my case I want to calibrate usrp with gnuradio as spectrum analyzer for
> the received signals.
>
> By measuring the correction factor between power(dBFS) in GRC to
> power(dBm) in a laboratory spectrum analyzer of the received signal.
>
> I used signal generator and in addition I've used my unique transmitting
> DUT.
>
> Do you think a noise source can be useful for my purpose?
>
> Thanks a lot
>
> Dor
>
> I guess if your spectrum analyser is calibrated, then a calibrated noise
> source is redundant.
>
>
> בתאריך יום ב׳, 3 ביולי 2023, 8:20 אחה״צ, מאת Marcus D. Leech <
> patchvonbr...@gmail.com>:
>
>> On 03/07/2023 12:24, Dor Ratz wrote:
>>
>> How are you Marcus?
>>
>> First, thanks a lot.
>>
>> I've done measurements for a specific Gain, frequency, temperature.
>> I've transmitted from a signal generator CW signal -> power splitter 1:2
>> to( spectrum analyzer and the USRP X310).
>> I first transmitted a CW, and then I transmitted another my system unique
>> signal.
>>
>> Can you please elaborate why you have suggested to use noise source? I'm
>> familiar with using it for Noise Figure measurements of DUT by using Y
>> Factor method, but I want to calibrate the power of signal between
>> Power[dBFS] in GRC to Power[dBm] presented in spectrum analyzer.
>>
>> Because a noise source is often better-calibrated than a narrowband
>> signal generator, and it kind of depends on what level
>> of spectral detail you want calibrated. If you want calibration steps
>> every few kHz, then a siggen may be a better fit.
>>
>>
>> I used RMS for [linear voltage] and after that 20*log(linear voltage) to
>> get Power[dBFS].
>> I understand that in the GNURadio flow graph everything is float-point
>> values in the range {-1.0,+1.0} and so I calculated power[dBFS] according
>> to 20*log10(1)=0[dBFS]
>>
>> I think the calibration was OK and I've found the correction factor
>> between Power[dBFS] in GNURadio to the Power[dBm] received in RX ANT
>> connector as was displayed in the spectrum analyzer at the same time by
>> using power splitter.
>>
>> As for saving complex\short to File Sink I'll update.
>>
>> Thanks
>> Dor
>>
>> [image: image.png]
>>
>> בתאריך יום ד׳, 28 ביוני 2023 ב-23:43 מאת Marcus D. Leech <
>> patchvonbr...@gmail.com>:
>>
>>> On 28/06/2023 16:35, Dor Ratz wrote:
>>>
>>> Hey Marcus,
>>>
>>> Thanks.
>>>
>>> Let me see if I get it right.
>>>
>>> Please see the attached gnuradio setup below .
>>>
>>> 1. Does the USRP pass with Wire Format=Automatic the int16 samples to
>>> the host computer? The ADC of X310 is 14 bits represented by 16 bits
>>> samples, so the maximal possible value in time domain for a strong
>>> enough signal is 2^(14-1)= (+-8192 ) ?
>>>
>>> NO! I've already said, the samples from the ADC are *scaled* before
>>> they hit the wire, into the wire format, which in this case
>>> is sc16.Further, the samples that "hit the wire" are *after* any
>>> manipulations by the DDC. The values on the wire
>>> can go from +/- 32767, although they rarely actually do.
>>>
>>>
>>> 2. So if I open the file sink (which was saved as short = int16) with
>>> python as int16 and look in python in the time domain:
>>>
>>>- In the time domain the maximal possible value is still (+-8192 ) ?
>>>
>>> Once the samples hit the GR flow-graph they are typically in
>>> {-1.0,+1.0}, and then you can specify scaling coefficients when
>>> you save them as complex int16.
>>>
>>>
>>>- In FFT, can I calculate Power[dBFS] according to
>>>20*log10(8192)=0[dBFS]?
>>>
>>> I strongly suspect that you're trying to do power estimation based on an
>>> empirical model, rather than by actual measurement
>>> with actual calibration equipment present.I have already said this
>>> is a bad approach, as have many others on this list.
>>>
>>>
>>>
>>> 3. If I want to open samples in QT GUI Sink as in the setup below, then
>>> can I do it as below with IShort to Complex block with scale factor = 8192,
>>> and then in the time domain in QT GUI Sink I will see :
>>>
>>>- In time domain - a float value with maximal possible value of
>>>(-+1) ? because it was normalized by 8192.
>>>- In FFT , can I calculate Power[dBFS] according to
>>>20*log10(1)=0[dBFS]?
>>>
>>>
>>> Thanks you,
>>>
>>> Dor
>>>
>>>
>>> [image: image.png]hugh
>>>
>>> [image: image.png]
>>>
>>>
>>> [image: image.png]
>>>
>>>
>>> [image: image.png]
>>>
>>>
>>> בתאריך יום ב׳, 26 ביוני 2023 ב-21:46 מאת Marcus D. Leech <
>>> patchvonbr...@gmail.com>:
>>>
On 26/06/2023 14:43, Dor Ratz wrote:
Thanks Marcus.
If so, then I can calibrate USRP -> GNURadio by writing down the :
- Power of the signal in FFT in [dB] -> convert to [dBm] by comparing
power when connected to a spectrum analyzer and changing Gain, frequency
